it's not an easy question but if you need that many clones at once you need more mothers - you should stick to 3 or 4 cuttings per mother at one time allowing a few days for recovery - environment is a big factor here - the healthier the plant the more slashing it will take -if it where me i'd keep 4-5 mother plants - and you'll want them at least a foot tall with shoots that are over 5 inches for best results .